What does fibrosis refer to?

Fibrosis specifically refers to the formation of fibrous tissue as a result of a healing process or chronic inflammation. This process involves the replacement of normal tissue with fibrous connective tissue, which may occur in various organs and can lead to organ dysfunction. In the context of healing, it is part of the body's response to injury, where collagen and other connective tissue components accumulate to repair damage.

The other options do not accurately describe fibrosis. Infection of connective tissue pertains to a pathological condition involving microbes, while displacement of tissue cells refers to a shift in positioning rather than the development of new tissue. Loss of muscle tone is related to muscle function rather than tissue formation. Thus, the definition of fibrosis is narrowly focused on the increase and formation of fibrous connective tissues, making it the correct answer in this context.